Global extensions used to be saved in folders inside
typo3/ext/, such as typo3/ext/news. In current
versions of TYPO3, this location should no longer be used. Instead,
use local extensions below typo3conf/ext/.

To convert a global extension to a local one, do the following:

Go to the Extension Manager.

Uninstall the global extension.

Delete the files of the extension from typo3/ext/, including
the directory of that extension itself.

Reinstall the extension from TER, which will put it into
typo3conf/ext/.

Note

In earlier versions of TYPO3 global extensions were an easy way of sharing
extensions between multiple TYPO3 instances. Nowadays the recommended way of
installing and maintaining extensions is via composer, where you may use
different strategies to achieve the same goal. One example would be to use
"path repositories"
in your composer.json file